Closure system

ABSTRACT

A pressure resistant seal for a metallic container is formed between a cylindrical portion having one end open and a cap which seals the open end of the shell. The cap is in the form of a frusto-conical flange which is inserted narrow end first into the open end of the shell and the container is sealed by means of a capping tool which pulls the flange against a die, deforming the flange and forcing the edge of the flange into the wall of the shell.

The U.S. Government has rights in this invention pursuant to ContractNo. DE-AC06-77RL01030 between the U.S. Department of Energy and RockwellInternational Corporation.

BACKGROUND OF THE INVENTION

This invention relates generally to the field of closures for metalliccontainers and more specifically to an improved pressure resistantclosure for a metallic container which is produced without heat.

Sealed metallic containers are used for the storage of many dangerous orreactive materials. When the contents of such a container are eitherextremely toxic or are radioactive, the seal of such a container must beair-tight and even pressure resistant. Most methods of making a pressureresistant seal on a metallic container involve the use of heat (e.g.welding). Such methods are unsuitable for sealing containers whosecontents are flammable, explosive, or otherwise reactive.

Radioactive materials, such as sources or waste products, need to behandled remotely to minimize worker exposure. Extremely toxic materials,such as certain pesticides, herbicides, and chemical warfare agents, aswell as biological agents and products of genetic engineering, alsorequire remote handling.

While the present invention is useful for forming a pressure-resistantstorage container for any type of material, the invention is especiallyuseful as an overpack for a leaking container of hazardous orradioactive material. Overpacking containers in current use range fromcardboard or plastic containers to metal 55 gallon drums. A moresophisticated overpack design is U.S. Pat. No. 4,100,860, whichdiscloses an overpack of laminar construction having a layer of foamedpolyurethane between its inner and outer shells.

One situation in which careful overpacking is especially important is inthe storage of cesium and strontium capsules. Cesium and strontium arebyproducts of the reprocessing of nuclear fuel. The surface dose rate ofcesium capsules can be as high as 15,000 R/hr and strontium capsules cangenerate as much as 500-700 watts of thermal power. Because of the highdose rate and heat production of the elements, it is desirable to removethe elements from reprocessing waste before any storage of that waste.Current practice for both elements is to encapsulate them in stainlesssteel and store the capsules under water, which provides both shieldingand cooling of the capsules.

If a capsule should develop a leak, the leaking capsule must beoverpacked with an external cannister to prevent the release ofradioactivity. Due to the high levels of radioactivity, such overpackingshould be done remotely and beneath the surface of the water. Theeffects of heat and of radioactivity make the use of any organic sealingmaterial impossible. Any water left inside the overpack will, byradiolysis, be broken down into hydrogen and oxygen, creating thepossibility of fire or explosion so the overpack seal must be both airtight and pressure resistant.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to obviate theabove-noted disadvantages by providing an improved method of andapparatus for the sealing of metallic containers that is simple to useand fabricate and can be used remotely.

Another object of the invention is to provide such a method of andapparatus that requires no heat and is air-tight and pressure resistant.

Another object of the invention is to provide such method and apparatusthat is resistant to damage from radiation.

The above objects are attained by utilizing a cylindrical containershell which is open at one end and a cap having a frusto-conical flangewhich is inserted narrow end first into the open end of the shell andfits closely therein. Force is applied to the flange of the cap,deforming it outwardly toward a more flattened position. The peripheryof the flange of the cap is thus pressed tightly into and deforms thewall of the cylindrical shell. This creates a tight seal which is gasand liquid tight and pressure resistant. The flange of the cap mustitself be deformed sufficiently to prevent its springing back when thepressure on it is released.

In more detail, the cap comprises a frusto-conical flange surrounding acentral stem. The cap is inserted into the container shell by a cappingtool which grips the stem. Force is then applied by the capping tool insuch a manner as to hold the container stable while forcing the capagainst a die, deforming the cap as has been explained above.

Other objects, advantages, and novel features of this invention will beapparent to those of ordinary skill in the art upon examination of thefollowing detailed description of a preferred embodiment thereoftogether with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical section of the sealed container shell and cap.

FIG. 2 is a vertical section of the container cap and capping tool.

FIG. 3 is a vertical section of the container shell, cap, and cappingtool before the container is sealed.

FIG. 4 is a vertical section of the container shell, cap, and cappingtool after the container is sealed.

FIG. 5 is a vertical section of the sealed container shell and cap witha storage container enclosed therein.

FIG. 6 is a drawing partially in section of a method of use of theinvention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

In FIG. 1 is shown a sealed metallic container generally designated 10,which is comprised of shell 12 and cap 14. Shell 12 comprises a wall 16with a closed end 18 and open end 20. Cap 14 which is inserted into theopen end 20 of shell 12 has a stem 22 and a frusto-conical flange 24surrounding stem 22. The wide end of flange 24 projects toward stemportion 22. Cap 14 forms a seal 26 with the wall 16 of shell 12. Thisseal 26 is a deformation of the metal of wall 16 of shell 12 and isproduced when flange 24 of cap 14 is forced into wall 16.

In one embodiment of this invention, the relative dimensions andthickness of cap and shell are selected such that this deformation iswithin the proportional limits for the metal of which wall 16 is formed.In this embodiment, if it is necessary to remove cap 14 to gain accessto the contents of this container, the capping tool can be used to applyforce to do so, and the wall of the shell will then return to itsoriginal configuration. In another embodiment, the deformation is withinthe limits of plastic deformation of that metal. In this secondembodiment, if the cap is removed by force, the wall of the shell willnot return to its original configuration.

In FIG. 2 is shown the cap 14 of the metallic container and capping tool28. Capping tool 28 has a pull-rod 30 which is attached to grippingfingers 32, which are constructed so as to grip stem 22 of cap 14. Pullrod 30 and gripping fingers 32 are moveably mounted within die 34 insuch a manner that when cap 14 is held firmly by gripping fingers 32 andthe pull rod 30 is moved relative to and in a direction so as to pullflange 24 of cap 14 against die 34. In FIG. 3 is shown cap 14 held bygripping fingers 32 of capping tool 28 and inserted inside containershell 12. Shell 12 rests against die 34 of capping tool 28.

In FIG. 4 is shown cap 14 held by gripping fingers 32 of capping tool28. Flange 24 of cap 14 has been deformed outward and a seal 26 has beenformed between the edge of flange 24 and the wall 16 of containers shell12. This has been accomplished by the application of force to pull rod30 which has been noved within capping tool 28 in such a direction thatflange 24 is pulled against die 34 deforming flange 24 outwardly to formseal 26 with container shell wall 16.

In FIG. 5 is shown sealed metallic container 10 comprised of shell 12and cap 14 being used as an overpack for a storage container fordangerous waste 36. In this embodiment, shell 12 has affixed inside thewall thereof retaining springs 38 which grip and hold the container ofdangerous waste 36 within shell 12.

FIG. 6 shows the manner in which the invention can be used remotely andunderwater. Capsules of cesium and strontium 40 are stored under waterin a storage basin 42. The storage basin itself has shielding 44. When aleaking capsule is located, a cover block 46 (removeable section of theshielding over the storage basin) is removed. Overpacking shell 10 isplaced open end down over the leaking capsule and nitrogen is bubbledinto the capsule, expelling water contained therein. The capping tool 28with the cap held therein, connected to a hydraulic pump, which is usedto apply force thereto, is placed on the bottom of the pool, with thecap of container 10 positioned so the narrow end of the flange pointsupward. The overpack shell which now contains the leaking capsule ispositioned over and lowered onto the cap. The hydraulic cylinder isactivated and the flange of the cap forced against the die of thecapping tool so as to form a seal with the wall of the overpack shell.Then the capping tool is removed and the overpacked capsule left in thestorage basin.

The foregoing description of the preferred embodiment of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and obviously many modifications and variations arepossible in light of the above teaching. It is intended that the scopeof the invention be defined by the claims appended thereto.

I claim:
 1. A method of sealing a cylindrical metallic container havinga open end comprising inserting within said open end a cap having afrusto-conical flange which fits closely within said container, thendeforming the flange of said cap in a direction tending to flatten it,thereby forcing the periphery of the flange of said cap into anddeforming said container so as to form a tight seal therewith.
 2. Anapparatus for producing a sealed metallic container comprising: acapping tool having a die, gripping fingers, and a pull-rod connected tothe gripping fingers, said rod and gripping fingers being movablymounted within said die; a metallic cap having a stem formed to be heldby the capping tool and, surrounding the stem a frusto-conical flange; ametallic shell having an open end; means for position said metallicshell with said open end surrounding said frusto-conical flange whilesaid stem is being held by said capping tool; and means for applyingforce to the pull rod of the capping tool.
 3. An apparatus as describedin claim 2 in which the relative dimensions of the flange of the cap,the diameter of the metallic shell, and the type of metal of which theshell is made are such that the deformation produced when the flange ofthe cap is forced by the capping tool into the wall is within the limitof plastic deformation for that metallic shell wall.
 4. An apparatus asdescribed in claim 2 in which the relative dimensions of the flange ofthe cap, the diameter of the metallic shell, and the type of metal ofwhich the shell is made are such that the deformation produced when theflange of the cap is forced by the capping tool into the wall is withinthe proportional limit for that metal shell wall.
 5. An apparatus asdescribed in claim 2 further comprising a second container suited tostore dangerous material, said second container being enclosed by thefirst-named container shell and cap after sealing, whereby, aftersealing, said first-named container shell and cap form an overpack forsaid second container.
 6. An apparatus as described in claim 5 furthercomprising: a plurality of retaining springs attached to the inside ofthe wall of the overpacking container.